1. Field of the Invention
This invention relates to a tarp cover arrangement for use in a transfer dump truck system, wherein a front tarp cover structure is used with the lead dump truck, and a rear tarp cover structure is used with each trailing dump trailer, the front and rear tarp cover structures being such that when they are in their uncovered conditions, the front portion of the trailing dump trailer of the transfer system may be introduced within the open rear end of the lead dump truck without disturbing either of the tarp cover structures.
2. Brief Description of the Prior Art
As evidenced by the Smith, et al., U.S. Pat. No. 5,143,496, it is well known in the patented prior art to provide a transfer dump truck system including a dump truck and one or more transfer trailers. The front dump box is mounted on the dump truck, and the rear boxes are mounted on their own trailer frames. A set of rails are mounted on the floor of the front dump box. The rear dump box(s) are mounted on a trailer with a similar set of rails. The front dump box is generally 96" wide and the rear dump box is generally 86" wide so that it can be inserted into the interior of the 96" wide box when transferring.
When the dump boxes are loaded and ready to dump, the driver releases the rear trailer from the front box, and dumps his load as normal. He then backs his dump truck up against the rear trailer where a set of male protrusions on the dump trailer match up with a set of female receivers on the front dump and the two lock together with a catch. The rear trailer has two axles and wheels on the bottom of the box which are controlled by electrical, hydraulic, or pneumatic motor means. When the trailers are locked together, the driver simply flips a switch on the rear of the rear trailers and the rear dump box travels forward into the interior of the front dump box mounted on the truck and a locking device holds the two dump boxes in place. This is the reason for the wider width of the front dump box and the narrower width of the rear trailer box.
The driver then dumps his load in the rear box, and then backs against the rear trailer frame and reverses the process described above. He then is ready to go back to his supply source to get another load.
The two main purposes for this type of dump transfer system is that one truck can now haul two types of loads (i.e., sand in the front dump box and rocks in the rear dump box) and it also allows the loads to be taken to areas where the maneuverability is limited (i.e., back yards, new construction areas, etc.).
It is also known in the art to provide tarp cover arrangements for open-topped truck containers to prevent the undesirable discharge of materials therefrom. Examples of such tarp cover systems are disclosed in the patents to Biancale U.S. Pat. No. 5,145,230 and Cramaro U.S. Pat. No. 4,189,178, wherein the tarp cover is supported by transverse bows or slots that ride upon the longitudinal side walls of the container. Drive means including a drive chain and sprocket driven by a hand crank to displace the tarp forwardly from an extended truck container covering position toward a collapsed condition in which the trailer is uncovered. These known tarp covering systems do not work satisfactorily on transfer dump truck systems owing to the limited clearance between the container walls when the rear box is transferred forwardly into the front box, since there is one inch or less clearance on each side when the rear box is introduced into the front box. Furthermore, the collapsed front and rear tarp covers and the drive means for the rear tarp cover would normally interfere with the complete introduction of the rear container within the front container.
The present invention was developed to avoid the above and other drawbacks of the prior art.